Despite what all the engineers and pump salesmen will tell you, there really are only two types of pumps; centrifugal and positive displacement. Understand the difference between these two and you are well on your way to understanding pumps. The difference is that centrifugal pumps spins at a high speed and transfers centrifugal or kinetic energy into the liquid in the form of velocity and pressure. The positive displacement pump, on the other hand, transfers a precise measured amount of liquid from the inlet to the outlet for each rotation or stroke of the pump. Let’s look at each.